um... English Bulldogs don't really have tail TO crop. They have a naturally short, cork screw tail. Some need to be amuptated as adults if the screw tail is very tight (for sanitation reasons), but a Pure bred EB would not have a tail long enough to crop. If it has a lond tail, it's not an EB.
Do you mean AMERICAN bulldog? If so, then no, I wouldn't crop it's tail.
Tail--The tail may be either straight or "screwed" (but never curved or curly), and in any case must be short, hung low, with decided downward carriage, thick root and fine tip. If straight, the tail should be cylindrical and of uniform taper. If "screwed," the bends or kinks should be well defined, and they may be abrupt and even knotty, but no portion of the member should be elevated above the base or root.